Character Frequency Counter

Given a string, count the frequency of each alphabet letter while ignoring case and excluding any non-letter characters. The result should be printed in the order that the letters first appear in the input.

For example, if the input is Hello World, the output should be:

h 1
e 1
l 3
o 2
w 1
r 1
d 1

Implement a solution that reads from standard input and writes to standard output.

inputFormat

A single line containing the input string.

outputFormat

For each alphabet letter that appears in the input string, output a line with the letter (in lowercase) and its frequency separated by a space. The lines must appear in the order the letter first occurs in the input.

## sample

Hello World

h 1
e 1
l 3
o 2
w 1
r 1
d 1

</p>